Heli-coil 1185-5CN312S Free Running Insert 5/16-18 500 Pack

Product Description

The HELI-COIL 1185-5CN312S is a tanged, free-running wire thread insert designed to restore or reinforce internal threads in parent materials that see repeated fastener engagement or vibration stress. Manufactured from 304 stainless steel, this insert provides corrosion resistance and long service life in demanding environments. It accepts a 5/16-18 UNC thread and has an overall length of 0.312 inches, corresponding to a 1D length-to-diameter ratio. Each insert features 4 free coils. Installation is performed with a dedicated HELI-COIL installation tool. This listing covers a package of 500 inserts.

Free-running inserts of this type are used across industrial, HVAC, plumbing, and mechanical service applications where stripped or damaged threads in aluminum, cast iron, or soft alloy housings need repair or where a stainless-steel thread form is needed in a softer parent material. They are installed by licensed mechanics, maintenance technicians, and field service professionals working on equipment housings, compressor bodies, pump casings, and structural brackets. The 5/16-18 UNC sizing is among the most common inch-series coarse thread standards encountered in trade work.

Key Features

• 5/16-18 UNC thread size for compatibility with standard inch-series coarse thread fasteners
• 304 stainless steel construction provides corrosion resistance and durability in harsh environments
• Tanged design for controlled installation with standard HELI-COIL tang break-off tools
• 0.312 inch overall length at a 1D length-to-diameter ratio suits standard thread engagement depths
• 4 free coils per insert for consistent thread form and load distribution
• Quantity of 500 inserts per package supports shop stock and production use

Compatibility

Designed for use in standard 5/16-18 UNC HELI-COIL prepared holes. Requires the corresponding HELI-COIL tap and installation tool for proper thread preparation and insert driving.

Installation Notes

Installation is typically performed by a machinist or qualified service technician using a HELI-COIL series tap to cut the oversized receiving hole, followed by a matched installation tool to drive the insert to the correct depth. Ensure the parent material is clean and free of chips or debris before insert installation. After seating, use a tang break-off tool to remove the driving tang where bottom-hole clearance requires it. Always verify thread engagement depth meets the fastener load requirements for the application before returning equipment to service.